robson



Sept. 11, 1956 ROBSON 2,762,223

OVERHEAT SAFETY CONTROL OPERATING MEANS Filed Oct. 29, 1954 Fig.5

INVENTOR. AUBREY H.R OBSON ATTORNEY United States Patent OVEREAT SAFETY CONTROL OPERATING MEANS Aubrey H. Robson, Rock Island, 11]., assignor to American Air Filter Company, Inc., Louisville, Ky., a corporation of Delaware Application October 29, 1954, Serial No. 465,569

8 Claims. (Cl. 74-2) The present invention relates to an overheat safety control for portable fuel furnaces and the like.

In portable heaters, it is desirable to provide some type of safety overheat control which will extinguish the flame of the heater by cutting off the fuel supply should the heater become too hot, or in case of flame failure. In the inexpensive type heater supplying liquid fuel by gravity flow to the burner, it is desirable to employ a mechanical safety control for this purpose, so as to avoid the expense of complicated electrical or fluid pressure controls.

An object of the present invention is to provide an overheat safety controller which is positive in action and is inexpensive to manufacture.

A further object is the provision of an overheat safety control which will shut ofi the supply of fuel upon overheating, and will not permit resumption of fuel fiow without manual intervention.

A further object is the provision of a simple safety control apparatus which will shut off the supply of fuel to the burner, should the temperature fall because the flame is extinguished, or should the apparatus overheat.

The invention will be described in greater detail in the following specification taken in connection with the accompanying drawing illustrating a preferred embodiment of the invention by way of example, and wherein:

Figure l is a side elevation of the invention;

Figure 2 is a plan view;

Figure 3 is an elevational view as seen from the right of Figure 1;

Figure 4 shows the invention applied to one form of portable heater; and

Figure 5 shows the invention applied to another type of portable heater.

Referring to the drawing, the control unit comprises a mounting base 1 in the form of a U-shaped plate having spacers 2, 2 suitably bolted thereto and guide straps 3, 3' bolted thereto, thus providing a channel for a slide 4. A temperature responsive element 5 of hairpin shape is fastened to one arm of the U-shaped plate by bolts 6 and its other end may be rounded as indicated at 7. A second temperature responsive element 8 of similar shape is similarly fastened to the U-plate by bolts 9, with its rounded end 11 lying adjacent the end 7.

The slide is biased downward by means to be later decribed, and near its top the slide carries an overhanging boss or book 12. In the position shown in Figure l, the end 7 of temperature responsive element 5 is beneath boss 12 and thus supports the slide 4 against the downward bias applied thereto. An increase in temperature causes end 7 to move to the left as indicated by an arrow, and movement to the right is limited by adjustable stop screw 13. The other temperature responsive element 8 at normal temperature is in the position shown in Figure 1 with its end 11 at the left, and end 11 moves to the right in response to increasing temperature as indicated by an arrow. A suitable stop screw 14 may be provided to limit movement to the right.

Temperature responsiveelements 5 and 8 do not respond equally to temperature changes. The response to temperature change is such that the end 11 moves to the right for a given increase in temperature more rapidly than end 7 moves to the left for the same temperature increase, so that at some predetermined temperature the end 11 will have arrived under boss 12 before end 7 has moved from under the boss. End 11 is slightly lower than end 7. Thus, when end 7 moves from under boss 12 the downward bias of slide 4 causes the boss 12 to engage end 11, which now resists the downward bias of slide 4, and end 7 can continue to move to the left.

The end 11 carries a U-shaped cross bar 15 which projects into the path of movement of end 7. After the end 11 has moved under boss 12 replacing end 7, a continued temperature increase will cause end 7 to continue to move to the left, until at some predetermined maximum temperature, end 7 will engage and move bar 15 to the left, thus withdrawing end 11 from under boss 12 and allowing slide 4 to drop in response to its bias. Slide 4 ordinarily is connected to a fuel valve to close the valve when the slide drops. The temperature now falls, end 7 moves to the right and end 11 moves to the left in response to the fall in temperature, but until the slide is manually raised, ends 7 and 11 cannot interfere with or restrain the slide any further.

Should the burner flame be extinguished accidentally or intentionally, the cooling of temperature responsive element 8 will cause the end 11 to retract to the left from boss 12, thus allowing slide 4 to drop to close the fuel valve. As end 11 is lower than end 7, it is not possible for end 7 to reenter under boss 12.

The application of the invention to a heater now will be explained. Figure 4 shows a conventional pot type of air heater using liquid fuel supplied by a pipe 15 to the pot burner 16. A blower 17 driven by a motor 18 forces air through a heat exchanger, and products of cornbustion escape by the stack 19. A thermostat control member 21, substantially as illustrated in Figures 1 to 3 is secured in the heated air stream near the stack, where it is subject to the heat of the stack, and a wire 22 or the like, including a fusible link 23, extends from slide 4 to the stem of valve 24 in the fuel line. To open valve 24 to start the flow of fuel, slide 4 is moved upwardly manually by means of a reset link 25 attached thereto. In the upper position slide 4 is held by end 7, thus holding valve 24 open against the bias of a spring in the valve. Should the stack become to hot the thermostat elements will release slide 4 as above described to allow valve 24 to close by the bias of its spring. Or, should the thermostat fail to function under overheat conditions, the fusible link 23 will break, thus allowing the valve to close. If desired, a modulating valve 26 may be provided in the fuel line, this valve being controlled by a thermostat 27 in the heated air outlet, to maintain a substantially uniform temperature of the heated air.

In the embodiment shown in Figure 5, the thermostat 21 is positioned in the heated air outlet of the heater, where it is subject only to the temperature of the heated air, and it serves to shut off the fuel supply where, after the heating operation has once been established, the air is either overheated or overcooled.

It will be appreciated that my safety control apparatus comprises: l) a control member 4, (a) which is mounted for manually imparted slidable movement from its lowermost or stop position, in which fuel valve 24 is spring biased to its closed position, upwardly through an intermediate run position to its highest or start position, and (b) which is (i) operative, during its upward movement between stop and start positions, to open valve 24, and (ii) operative, in its start and run positions, to hold valve 24 open; (2) a slow moving thermostatic starting elements, (a) which is mounted for slow horizontalmovement, "from "a starting position through a 7 running position to an overheat position, in response to an operating temperature rise from a low starting temperature range through a "higher running temperature range upwardly to an overheat temperature value and (b) which is (i) operative, in its starting :position, to permit control member 4 to move upwardly into its highest 'or start position and to latch it therein, and (ii) operative, V as it moves out of its starting position, to unlatch the against -a'=bias urging its return to its stop positionyastart start position, and (iii) operative, inits running position, to catch control member 4, when it drops from its start position, and to latch that member in its run position; said control member 4 also being operative in its run position to block the return'ofthe starting element 5' to its starting'position; and (4) safety means op'er- V ative, in response to the horizontal movement of the starting element 5 from its running position to its ?overheat position, to engage and move said running element 8 out of its running position, inwhich itlatches member 4, and thereby permit member 4 to drop from its intermediate run positionto its stop position.

I claim asmy invention:

1. A safety control apparatus comprising: a member adapted to be biased in one direction; thermally responsive detent meansrestraining'movement'of'saidmember .in said one direction, and adapted upon increase in temperature to move out of restraining position; a second thermally responsive means normally out of restraining position and adapted by increase intemperature to move into restraining position of'saidmember; and means connecting said first and second thermally responsive means for mov-' ing said second thermally responsive means out of restraining position upon continued movement of the first thermally "responsive 'detent means.

2. An apparatus asspecifiedjnclaim 1 wherein: said first temperature responsivemeans extends beyond the second temperature responsivemeans to hold said member beyond the second means.

3. An apparatus as specified in claim 1. having: a valve connected'to said member and adapted to be closed upon movement of said member insaid one direction.

4. An apparatus as specified in members each having a movable'end, said ends being movable in opposite directions in response to a temperature change.

5. An apparatus as specified in claim 1 wherein said second mentioned thermally responsive means moves more rapidly than the first mentioned thermally responsive means in response to a predetermined temperature change. 7 7 p p 6. A safety controlapparatus comprising: a control member mounted for manual movement from a stop position through a run position to a start position ing element mounted for movement in response to 'a rising temperature from a'low temperature starting position through an intermediate temperature stunning position to a high temperature overheat position and being operative, in .its starting position, to permit movement of said control member into its start position and to block its return movement therefrom; said control member being operative in its run position to block the return of said starting element into its starting position; and a running element mounted for movement in response to a rising temperature from a low temperature starting position to-an intermediate temperature running position and.

being operative, upon such temperature rise, 'to'reach its running position before the starting element has entirely left its starting position and being further operative, when the starting element leaves the starting position sutliciently to release the control member, to stop the return of the control member at'its run position. i 7. The apparatus of claim oincludingz safety means,

7 operating in response to the movement of the starting element from its running position to its overheatiposit'ion, to move said running element out of its running position so as to permit said control member to return to its stop.

said running element moves laterally toward said control member under rising temperature conditions below the running temperature.

References-Cited in the file ofthis patent V UNITED STATES PATENTS f 2,013,798

2,249,887 Dayton July22, 1941 claim 1 wherein said thermally responsive "means comprises hairpin shaped Yanochowski Sept. '10, I935 

